Regulation of EBV lytic cycle gene expression may have important and underappreciated clinical significance for EBV-related malignancies and diseases. EBV establishes a latent infection in B-lymphocytes that can be disrupted by transcriptional activation of the viral immediate early genes BZLF1 (Zta) and BRLF1 (Rta). The EBV genome exists as a nucleosomal episome during latency, and histone deacetylase inhibitors are potent stimulators of viral lytic gene expression. Reactivation correlates with histone hyperacetylation at the Zta and Rta promoters, further indicating the importance of chromatin modification in controlling the switch from latent to lytic transcription. In this application, we propose to test the hypothesis that EBV reactivation is regulated by chromatin modifications. Our preliminary data suggests that the Zta promoter is actively repressed by a histone deacetylase (HDAC)-associated corepressor that can be relieved by CBP/p300 histone acetylase (HAT) activity. Specific aim 1 will investigate the regulation of the Zta promoter by chromatin modification and remodeling. We have also found that CBP potentiates Zta transcription activation in a complex and promoter-dependent manner. Specific aim 2 will investigate the mechanisms of CBP transcriptional coactivation of Zta. Finally, we have found that Zta stimulates the nucleosome-specific HAT activity of CBP by a mechanism that we believe is novel and highly significant. Specific aim 3 explores the biochemical basis and biological significance of Zta mediated stimulation of CBP HAT activity. These aims should provide information important for EBV regulation of lytic cycle gene expression, in particular, and for eukaryotic transcription regulation, in general.